Purpose

This work deals with the application of a solidification/stabilization process with the aim to obtain safe and reusable granular materials from a polluted soil and to elucidate the mechanisms involved in the retention of several heavy metals.

Materials and methods

The High Performance Solidification/Stabilization (HPSS®) process was applied to the selected contaminated soil by using both ordinary Portland cement and calcium aluminate cement, as well as several binders prepared by combining these two types of cement in different proportions. Leaching and mechanical tests were carried out to evaluate the performances of the proposed binders in the pellets produced by the HPSS® process, while XRD analysis and SEM/EDX imaging were used to investigate the phase composition and internal microstructure of the treated samples.

Result and discussion

The examination of the obtained granular materials revealed that the immobilization of Sb was mainly related to its inclusion within calcium silicate hydrates’ structure; the immobilization of Cr, Pb, Ni, Co, Zn and Tl was associated with the eluate pH and their incorporation within ettringite structure, while for Se, Cu, Ba and V, the main retention mechanism was physical encapsulation. In addition, the application of a wet conditioning process improved the materials’ performance, leading to granules always satisfying the Italian regulatory requirements for reuse.

Conclusions

The findings obtained in this study were useful to better elucidate the mechanisms involved in the retention of heavy metals by several binders, contributing to the development of sustainable management strategies for contaminated soils and sediments through their transformation into reusable materials.

Graphical abstract

中文翻译：

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铝酸钙水泥替代普通波特兰水泥以修复重金属污染的土壤：机理和性能

目的

这项工作涉及固化/稳定化工艺的应用，目的是从受污染的土壤中获得安全且可重复使用的颗粒材料，并阐明保留几种重金属的机理。

材料和方法

通过使用普通波特兰水泥和铝酸钙水泥，以及通过将这两种类型的水泥以不同的比例混合而制备的几种粘合剂，将高性能固化/稳定化（HPSS®）工艺应用于选定的受污染土壤。进行了浸出和机械测试，以评估所提出的粘合剂在HPSS®工艺生产的颗粒中的性能，同时使用XRD分析和SEM / EDX成像技术研究了处理样品的相组成和内部微观结构。

结果与讨论

对获得的颗粒状材料的检查表明，Sb的固定化主要与它被包含在硅酸钙水合物的结构中有关。Cr，Pb，Ni，Co，Zn和Tl的固定化与洗脱液的pH以及它们在钙矾石结构中的结合有关，而Se，Cu，Ba和V的主要保留机制是物理包封。此外，湿法调理工艺的应用改善了材料的性能，使颗粒始终满足意大利法规对再利用的要求。

结论

这项研究中获得的发现有助于更好地阐明几种粘合剂对重金属的保留所涉及的机制，通过将污染的土壤和沉积物转化为可重复使用的材料，有助于发展可持续的管理策略。

图形概要